Development of distributed and self-organized physical cell identity assignment schemes for LTE-advanced systems

A major challenge pertinent to Long Term Evolution (LTE) systems is the development of self-organized PCI assignment solutions. This paper focuses on this challenge and proposes a new distributed and self-organized solution named Stable Graph Coloring (SGC) scheme. The proposal introduces a temporal PCIs sub-range for newly switched on eNBs, minimizes the impact of Neighbor Cell relations (NCRs) inaccuracy and re-uses PCIs as most as possible. It is evaluated compared to 3 known distributed approaches, namely the Graph Coloring (GC) approach, the LTE standard proposal and the Nokia-Siemens (NS) approach, by means of simulative studies. The studies investigate the impact of network size and the capabilities of stabilizing LTE systems. Our results show that the SGC scheme is slightly outperformed by the NS approach when considering the average number of PCIs conflicts. For the PCIs utilization ratio, the SGC approach is considerably better than the NS scheme. The most important result our proposal realizes is the capability to converge to a steady state while carefully utilizing the PCIs (less than 70% for high densities). Networks with such densities lose their stability when employing the LTE standard proposal and the NS approach.